1. Field of the Invention
The present invention relates to monolithic vibrating beam force sensors (resonators) and more particularly to their use in vibrating beam pressure transducers and vibrating beam accelerometers in which the proof mass, the proof mass suspension system and the resonator are made from a single piece of quartz crystal.
2. Description of the Prior Art
U.S. Pat. No. 5,109,175 titled Monolithic Resonator for Vibrating Beam Force Sensors describes a three dimensional monolithic resonator structure where the basic sensing element is a vibrating beam that changes its frequency of vibration in response to axial force. The two primary applications described for the prior art invention are for accelerometers and pressure transducers. For the accelerometer application, the source of axial force is a proof mass reacting to an input acceleration being measured. For the pressure transducer application, the force on the resonator is caused by a bellows which responds to an applied pressure being measured. The primary innovative feature of the prior art structure is that the sensing portion of the structure, consisting of the vibrating beam and its vibration isolation mechanism, has a much thinner cross-section than the outer structure. Thus, the monolithic structure has two thicknesses which permit the inner portion of the structure to be as thin as necessary for sensitivity requirements, while the outer portion of the structure can be as thick as necessary to have the required mass or stiffness necessary for its application.